Intracranial Atherosclerotic Disease

Table 2

Comparison of nonimaging modalities in the detection of intracranial stenosis.

Modality	Degree of stenosis	Sensitivity	Specificity	Limitations
Digital subtraction angiography				Invasive test: Procedure risk rate: 0.3% for all complications, 0.03% for stroke [56]
MRA (TOF) [54] for ICA disease	50%–69%	37.9%	92.1%	Limited spatial resolution, flow signal intensity loss as a result of saturation or phase dispersion, susceptibility artifacts near sphenoid sinus, and over- and underestimation of stenosis due to dephasing artifacts
	>70%–99%	91.2%	88.3%
	ICA occlusion	94.5%	99.3%
MRA (TOF) 3T [57]	50%–99% stenosis	78%–85%	95%
	Occlusion	100%	99%
MRA (CE) [54]	50%–69%	65.9%	93.5%
	>70%–99%	94.6%	91.9%
	ICA occlusion	99.4%	99.6%
CTA* [59]	Stenosis^‡	98%	99%
	Occlusion	100%	100%
Transcranial Doppler Ultrasound [62]	>50% stenosis or occlusion			High level of technical and procedural skill is required to obtain the best quality images. Reliable insonation of the posterior circulation is particularly difficult
	For MCA stem (M1)	90%–99%	90%–99%
	For intracranial segment (V4) of vertebral and basilar artery	70%–80%	90%–99%
CDDI [61]	Atheromatous pseudo-occlusion
Unenhanced^†		70%	92%	False negative rate 30%
Echo-enhanced PFI		83%	92%	False negative rate 17%
Unenhanced		95%	92%	False negative rate 5%
Echo-enhanced		94%	100%	False negative rate 6%

CDDI: Color Doppler-assisted duplex imaging, PFI: power-flow imaging.
*Data are percentages using DSA as the reference standard.
^‡North American Symptomatic Carotid Endarterectomy Trial (NASCET) criteria were used for stenosis calculations: [(𝐷_𝑛−𝐷_𝑠)/𝐷_𝑛]×100, where 𝐷_𝑛 is normal diameter and 𝐷_𝑠 is stenosed diameter. NASCET stenoses were grouped according to the following grading scale: normal (0%–9%), mild (10%–29%), moderate (30%–69%), severe (70%–99%), or occluded (no flow detected). Normal (0%–9%) and mild (10%–29%) stenosis were not considered diseased vessel segments and were excluded from analysis.
^†Ultrasound emission energy and gain cannot be increased high enough without the appearance of disturbing acoustic noise that diminishes the reliable depiction of orthograde flow signals.